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Testing "Large" Capacitors

12-20-2013, 08:31 PM

I have a basically new set of capacitors from an AM band transmitter station. I know how to test air conditioning capacitors that are typically in the range of 25-75 uF on AC up to 370 volts. My meter will do this.

These are DC capacitors, polarity is marked, with the following information:

36DX 95*C
15,000 uF 100v

0836L 46
+ Positive

Made by Nippon Chemi-con

I also have some that are 5140 uF at 300 volts and some others at 400 volts.

Is there a way to safely test the viability of these without killing myself? I'd rather not have to yell "CLEAR!" when testing these either.

Comment

thanks. i didnt know there was a dedicated tester available in an affordable range for the average consumer. the amprobe model looks like it's probably the best fit for not only my hvac work but for the capacitors from the transmitters.

from what i read earlier the only thing i cant test for is the voltage leak when at the full voltage rating. i dont suppose it matters much for me though.

It sounds like you have a bunch of electrolytic capacitors which are polarity sensitive. I'm not 100% clear on the specifics but it is not realistic to achieve these high capacitances with non-electrolytic capacitors - they would get too large. My guess is that they came out of some of power supplies - usually that's the main place such large capacitors are used.

Like many analog components capacitors tend to degrade with age and I have seen capacitors read the correct value during measurement but malfunction when operating voltage is applied so getting the correct reading on your meter is no guarantee that they are in good shape and will operate correctly when in the actual circuit.

Comment

I dont have any plan for these at the moment. They are all electrolytic, though the older ones by a different manufacturer are much lighter than the newer and also sound hollow. There are no visible leaks on any of the older ones and they are all the same weight.

I was looking into a high wattage synched camera strobe kit. The charge circuit was voltage tunable and can be synched via tach cord or light pulse. All the parts would be less than $55 and the company selling the kits verifies operation and/or adjusts the components to work with any given capacitor.

That got me to thinking, what would it take to keep a xenon tube lit all the time in the same fashion as a fluorescent tube. I havent gone much past the heat dissipation part of that though.

Comment

Unfortunately I'm not familiar with the Xenon strobe type lamps and the circuitry used to power them. However one suggestion I have that you could try would be to couple the trigger signal to an oscillator that runs fast enough so that the flash rate would cause the lamp to seem to be on. That is one technique that would allow you to either "turn on" the lamp using the oscillator or trigger it manually.

The simplest timer circuit could be made of something like the well known 555 timer chip - it is not very accurate as it depends on a charge/discharge cycle of an RC network coupled to the chip but it would be good enough for something like this.

Of course I'm not familiar with the circuit for flashing the Xenon so I'm not sure that a high flash rate may be enough time for the caps to recover. Your reference circuit/it may have some info on this.

Comment

I dont have any plan for these at the moment. They are all electrolytic, though the older ones by a different manufacturer are much lighter than the newer and also sound hollow. There are no visible leaks on any of the older ones and they are all the same weight.

I was looking into a high wattage synched camera strobe kit. The charge circuit was voltage tunable and can be synched via tach cord or light pulse. All the parts would be less than $55 and the company selling the kits verifies operation and/or adjusts the components to work with any given capacitor.

if they sound hollo

That got me to thinking, what would it take to keep a xenon tube lit all the time in the same fashion as a fluorescent tube. I havent gone much past the heat dissipation part of that though.

be very careful with them
research their number and manufacturer for the construction and composition as they may contain oil with pcb's

shooting the s*** is a lot more fun when you use hollow points (much more splatter)